Regional enteritis (RE), ulcerative colitis (UC), and gluten sensitive enteropathy (GSE), are diseases of the gastrointestinal tract in which immunological factors may play a major role in the pathogenesis. Using the technique of organ culture, it is our objective to study the intestinal mucosa of these patients and determine if the biochemical, morphologic, and immunologic behavior of tissue from patients with these diseases is different from that of intestinal tissue from normal subjects. Tissue parameters to be measured include rates of protein, glycoprotein, and immunoglobulin synthesis, brush border enzyme activity, and tissue morphology at the light and electron microscope levels. We will relate these parameters to the patients' clinical condition (remission, exacerbation, and treatment). Intestinal tissue will be cultured in the presence or absence of cortisol or azulfidine, as well as intestinal secretions, isolated peripheral blood and intestinal lymphocytes and serum obtained from patients with these diseases and normal subjects. The effect of these added materials on the above parameters will be determined. Additionally, we will culture rectal tissue from patients with active ulcerative colitis in the same culture dish with rectal tissue from patients with inactive ulcerative colitis to determine if the tissue from the patient with active disease alters the biochemical, immunological and morphologic behavior of the tissue from the patient with inactive disease. The effect of gluten fractions added to the culture media of specimens of small intestine obtained from patients with GSE will be studied in an effort to identify the specific fraction of gluten causing the intestinal lesion. The ability of gluten fractions to elicit production of antigluten antibodies will be studied, and antigluten antibodies will be used in organ culture to attempt to reproduce the intestinal lesion. Histocompatibility antigens in patients with GSE will also be examined.